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Investigations of dilute magnetic material HgTe:Cr
|Valeriy V. Asotski 1, George V. Lashkarev 1, Mykhailo V. Radchenko 1, Vasiliy M. Frasunyak 2|
1. Institute for Problems of Materials Science, 3, Krzhizhanovsky, Kyiv 03142, Ukraine
The doping of semiconductors by d-elements impurities enables to operate with their characteristics, in particular with their magnetic and kinetic properties. The behaviour, differences of action of Cr impurity and its effect on properties of HgTe are shown. The nature of defect states is discussed. Magnetic susceptibility (MS), specific resistivity, Hall coefficient R, thermoelectromotive force α and electron spin resonance (ESR) of HgTe doped by Cr in the region 4.2÷350 K in magnetic fields up to 7 kOe were investigated. Electron concentration was (6÷25)·1016сm-3 at 4.2 K. General concentration of chromium doping impurity was in limits of 2÷50·1018 сm-3. The investigation results of R(T) in HgTe:Cr show a presence of a peculiarity at T~25 K. A magnitude of effect increase with Cr concentration increase. It may be explained by existance of resonance acceptor Cr-level near a bottom of conduction band. Thermoelectromotive force of HgTe:Cr had an extraordinary temperature dependence - a saturation at T>150 K. This may be explained by action of two competition mechanisms: increase of α~T, lnT and decrease of α~n-2/3, (α0-lnn), where n~exp(-ε/kT). Temperature dependence of MS of HgTe:Cr show the presence of additional paramagnetism, which does not depend from temperature, grow with increase of Cr concentration and can be considered as paramagnetism Pauli of ions Сr2+. At high concentration the Cr impurity leads to occurrence of orientational paramagnetism, which increase with temperature decrease. The exchange interaction between the magnetic centres is absent and the mechanism of single introduction of impurity atoms in a lattice is observed. Absence of ESR signal which is obliged to chromium testifies that almost all Cr is in nonmagnetic state. The Cr ion has a configuration Cr2+(d4), which leads to Van-Vlek paramagnetism independent from temperature.
Presentation: Poster at E-MRS Fall Meeting 2006, Symposium E, by George V. Lashkarev
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-16 09:27 Revised: 2009-06-07 00:44